Posted
by
Hemos
on Monday March 26, 2007 @10:49AM
from the power-UP dept.

BobB writes "St. Louis University researchers have concocted batteries fueled by almost any kind of sugar, from tree sap to flat soda, and that could be used to power everything from computers to cell phones. Their thinking: If sugar can jack up the human body, why not electronics?"

There's better coverage of the story at Physorg [physorg.com] (via Engadget).

Question: If the fuel cell contains enzymes, couldn't a 2-stage fuel cell be created that has cellulases, thus making waste switchgrass/etc. a potential direct fuel? Why would we need to even bother with cellulosic ethanol then? Or is this even possible?

No, autos are the least interesting reason to invent new batteries. Automobiles need energy dense, quick to charge batteries far more then they need eco-friendly batteries. Don't get me wrong, environmentally friendly batteries would be nice, but that means starting over at square one with a new technology. It is far more likely that we will be able to squeeze enough out of an old technology by modifying it in some way to achieve what we need. The eco-friendly stuff will come after the roads are clogged with less-then-friendly battery powered cars.

The bad thing about using cellulosic materials directly is that they tend to resist being broken down into sugar while they are in their raw/natural state. They need to be pretreated, which usually involves some combination of grinding, heating, soaking, 'steam explosion' (quick pressure release), to obtain a reasonable yield of sugar. If you don't pretreat the feedstock, you won't get nearly as much sugar, and you battery will be bigger because you're only using X% of the initial material. And if you use pretreated material in your battery, why not just convert the cellulose to sugar outside the battery, wher you can better control the reaction conditions and yields? Plus, the enzymes needed to convert the cellulose to sugar and the sugar to electricity may need different reaction conditions, as enzymes are often picky about their pH, concentrations, temperatures, co-reactants, etc.

The potato is providing none of the energy in that example. The galvanic potential [wikipedia.org] between the electrodes is what is producing the electricity. The potato is an electrolyte in (relatively) solid form. In the battery from the article the sugar is actually consumed to produce the electricity, whereas the potato isn't.

True, but I for one am highly interested in an energy-dense, high discharge capable battery for cars. Something that can store a couple tens of kWh and let it go at a kW rate (stated in Watts, as I couldn't guess the voltage, and thus amperage resuired for such power outputs) in a package that's volumetrically similar to a regular sedan fuel tank (10-15 gal).

But there are many reasons to have EXTREMELY low powered devices. Pacemakers, implantable drug pumps, insulin sensors. Each time you have equipment that can power itself by using a little bit of its environment, it means you don't have to go out and change the batteries. It also means that you worry less about battery leakage, since it's powered by the ambient medium.

Granted, sugar powered (alcohol powered, gas powered etc etc) fuel cells are old news. They've been able to make these little buggers for years. However, the hard part is making them cheap and reliable. I wish them luck.